1. Field of the Invention
The present disclosure relates to a radiation imaging apparatus and radiation imaging system.
2. Description of the Related Art
There has been proposed an arrangement in which a radiation imaging apparatus detects the presence/absence of irradiation with radiation to synchronize a radiation generating apparatus and the radiation imaging apparatus. Japanese Patent Laid-Open No. 2002-543684 has proposed a radiation imaging apparatus which detects the presence/absence of irradiation with radiation by using the fact that when the radiation imaging apparatus is irradiated with radiation, a current flows through a bias line which supplies a bias potential to pixels. More specifically, when a current flowing through the bias line exceeds a predetermined threshold, it is determined that the radiation imaging apparatus has been irradiated with radiation. In addition to a current arising from radiation, a noise current flows through the bias line owing to various factors. When the noise current is large, it may be erroneously detected that the radiation imaging apparatus has been irradiated with radiation though it is not actually irradiated with radiation. To prevent the detection error, in the above-mentioned reference, a sample and hold circuit is arranged to hold a dark current flowing through the bias line. A value obtained by subtracting the held dark current from a current flowing through the bias line at a certain time point is compared with a threshold.